The present invention relates to an improved tripping device for thermal relays, which is specially designed to maintain at all times a constant pressure over the electric contacts until they are tripped.
Basically there are two types of electric switches, that is trigger and rocker switches. The trigger type switches permit the contact pressure of the electric terminals to be maintained until they are tripped from the contact position to the inoperative position or vice versa. However, this type of switch cannot be adapted to automatic controls, so as to be operated by thermal relays and similar elements. Rocker type switches are suitable to be operated by means of automatic elements, but the contact pressure is not maintained constant, since as the rocker moves, the pressure between the electric terminals is gradually reduced until it reaches a point whereat the pressure is zero, from which point the switch is triggered. This gradual reduction in the pressure between the electric contacts causes serious heating problems in the terminals, as a result of which the application of this type switch is restricted to low-power equipment, since otherwise the heating results in risks and could cause serious accidents.
In view of the aforegoing, it is clear that it would be advantageous to have a switch which maintains the contact pressure constant and which can operate with automatic systems without any limitation in the power due to heating effects. The ideal solution to overcome the problem resides in a switch which combines the action of a rocker with a sliding strip or bar which bears the electric contacts, and this is precisely the solution offered by the present invention.